There just might be a secret behind Josh Donaldson’s hot hitting of late, and he revealed it after the A’s 8-3 loss Monday to the Angels: Donaldson has been using teammate Chris Carter’s bats ever since he was recalled from the minors Aug. 14.

“I didn’t have any bats when I first came back,” said Donaldson, who has had three big league stints this season. “I picked up one of Carter’s and asked if I could use it. Obviously I started hitting the ball pretty well. … I’ve been using his the entire time.”

Carter’s bats are made by Old Hickory — 34 1/2 inches, 32 1/2 ounces. What does Donaldson like about them compared to his own? “It’s a little bigger barrel, a little heavier, same length. Obviously I like the bat.”

Donaldson broke one of them early on and asked Carter if he could use one of his batting-practice bats. Donaldson has stuck with that one. He has since ordered his own batch of bats — same as Carter’s — that are on the way.

Donaldson and Carter have something else in common — they are both contributing some big power numbers for the A’s. Donaldson has four homers in his past five games and is hitting .338 with 15 RBIs in 19 games since being recalled from Triple-A Sacramento. “He’s got a lot of confidence going right now,” A’s manager Bob Melvin said. “The ability is certainly there and I think the confidence is finally going along with it. We’re getting a lot of production down toward the bottom of the order, where we feel we have a chance to pop one no matter where we are in the lineup.”

Carter has homered four times in his last eight games and has 14 homers since he was recalled June 29. As a team, the A’s have a major league-leading 74 homers since the All-Star break.